In process automation technology, one works with many different sensors. Thus, there are sensors, which sense fill level, conductivity, pressure, temperature, angular setting (e.g. on a machine) or pH-value, as well as applications such as optical sensors, which are embodied, for example, as turbidity sensors or absorption sensors. Also ion-sensitive sensors are applied, which sense, among other things, the nitrate content of a liquid. In order to process the input signals of these different sensors, a measurement transmitter is known, in the case of which these sensors are each connected to an adapter via a transmission line having a low transmission rate. The adapter is, in turn, connected via a central bus system with a central processor, wherein the bus system has a high transmission rate. Data are exchanged between the sensors and the processor bidirectionally via the adapter, wherein the adapter converts the high transmission rate of the bus system into the low transmission rate of the transmission line of the sensor and vice versa. In such case, for the most part, digital sensors with different protocols and transmission rates are used.
The bus system has only one channel to the adapter, which, thus, can connect the processor with only one sensor. That means that the processor can query, or communicate with, the sensors only one at a time. In the case of a large occurrence of data, the sensors influence one another in the query loop, which has a limited amount of time and, because of the slow working adapter, overlaps occur in the data transmission.
Moreover, the software, which runs in the processor, is modified during the manufacture of the measurement transmitter to match the predetermined number of sensors to be connected and the selected types of sensors.